Diabetes affects nearly 26 million individuals in the U.S, and if current trends continue, 1 of 3 adults will have diabetes by 2050. Diabetes self-management education and support (DSME) is a cornerstone of effective care that improves clinical control and health outcomes; however, DSME participation is low, particularly among underserved populations, and ongoing support is often needed to maintain DSME gains. The complex needs of individuals with diabetes cannot be adequately addressed in the typical 15-minute primary care visit. By adopting a team-based approach that is informed by the Chronic Care Model, other primary care personnel [e.g., medical assistants (MAs)] can be trained as health coaches to work in tandem with primary care providers to deliver self-management support. Although research is limited, several studies have shown that MA-provided self-management support improves outcomes in diabetes. The proposed cluster-randomized, controlled, pragmatic trial will compare the effectiveness of MA Health Coaching (MAC) with usual care (UC) in improving diabetes clinical control among 600 individuals, aged 18 and older, with type 2 diabetes mellitus (T2DM), and glycosylated hemoglobin (HbA1c) = 8.0%, and/or low-density lipoprotein cholesterol (LDL-C) = 100 mg/dL, and/or systolic blood pressure (SBP) = 140 within the last 60 days The study will take place within primary care clinics of two health systems that serve large, ethnically/racially, and socioeconomically diverse populations in San Diego County: Neighborhood Healthcare (a FQHC) and Scripps (a large, non-profit, private insurance-based health system). One clinic within each system will be randomly allocated to MAC, and one to UC. In addition to usual care, MAC clinics patients will receive brief, targeted self-management support from the MA Health Coach. The MA will be afforded flexibility in their implementation of MAC elements (i.e., health behavior assessment, medication reconciliation, motivational interviewing, agenda- and goal-setting, problem- solving, closing the loop techniques to ensure understanding of recommendations), and will tailor their use of these components to patient-specific needs and priorities. As needed, MAs will coordinate brief phone follow- up to review progress and problem-solve around any barriers. Electronic health records will be used to identify eligible patients and to examine change in diabetes clinical outcomes (HbA1c, LDL, SBP) over 12 months. Changes in patient-reported behavioral (diabetes self-care) and psychosocial (quality of life, patient activation) outcomes will be evaluated by phone assessment in a subset (N=300) of MAC and UC participants at baseline, and months 6 and 12. An evaluation guided by the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework and an examination of program costs will assess potential for sustainability and scalability. The MAC program offers a potential solution to the burgeoning primary care demand-capacity imbalance that can be applied in diverse healthcare settings to better address the needs of the growing number of individuals with T2DM.